1. The Field of the Invention
The present invention relates to the field of high-speed data communications. In particular, the present invention relates to a circuit and method for amplifying a laser signal.
2. Description of the Related Art
In high speed optical communication systems, laser signals may be used to transmit information. For example, a laser signal, transmitted by a remote device, may be detected by a photo detector, amplified by a trans-impedance amplifier circuit, and filtered by a filter circuit. After the laser signal is filtered, it is then amplified by an amplification circuit and converted to a digital format for further processing or storage.
Traditionally, the amplification circuit may be implemented with differential amplifiers consisting of pairs of transistors. One of the design goals of the amplification circuit is to decrease the settling time of the laser signal during a signal transition. This design goal may be accomplished by using a differential amplifier having a higher amplification gain to drive the laser signal in order to ensure a fast signal transition. Another design goal of the amplification circuit is to minimize the electromagnetic interference created by the higher order harmonics of the laser signal during signal transitions. This design goal may be accomplished by using a differential amplifier having a lower amplification gain to drive the laser signal. As a result, a design tradeoff has to be made to choose between having a higher or lower amplification gain. The design is comprised because it has either the adverse effect of electromagnetic interference or lower design margins for signal settling time during signal transitions. The adverse effect of electromagnetic interference may lead to additional system costs employed to reduce the interference problem. The adverse effect of lower design margins for signal settling time may lead to lower signal quality and may also lead to transmission errors.
Therefore, there is a need for a laser amplification circuit which can increase the settling time margin during signal transitions and at the same time minimize the electromagnetic interference generated from such signal transitions.